The somatosensory cortex of adult rodents contains barrel-like aggregates of neurons that respond selectively to discrete, angular displacements of single vibrissae (whiskers) on the contralateral face and in some cases to patterned stimuli involving sequential displacements of multiple whisker hairs. These functional properties reflect the discrete nature of the thalamic input to the barrels as well as excitatory and inhibitory connections among cells within the cortex. Preliminary studies indicate alterations in cortical metabolic activity and receptive field characteristics of barrel neurons following chronic whisker trimming from birth. The proposed project will evaluate the role of natural sensory input in the development and maintenance of the normal organization of the rat SmI barrel cortex. Proposed experiments will: a) use electrophysiological techniques to characterize quantitatively alterations in receptive field properties of single cortical units in adult rats subjected to chronic whisker trimming from birth, and b) test the hypotheses that alterations in cortical metabolic activity and cortical receptive field properties reflect changes in specific thalamocortical relations and/or the number and distribution of intracortical inhibitory interneurons and their processes. These hypotheses will be examined using conventional neuroanatomical and immunocytochemical techniques. The proposed experiments will provide important information concerning the anatomical and physiological organization of the mammalian central nervous system, especially in regard to the influence of altered sensory experience on the functional development of the cerebral cortex.